Method and device for transmitting and receiving message by v2x terminal in wireless communication system

ABSTRACT

A method for transmitting data by a UE in a wireless communication system, according to an embodiment of the present invention, comprises the steps of: transmitting a first message through time-frequency resources; and, if a UE must transmit a second message which is related to the first message, transmitting the second message through a frequency resource region which is the same as a frequency resource region in the time-frequency resources after predetermined time from the time-frequency resources, wherein the predetermined time is determined on the basis of bits selected from a plurality of bits by means of the UE, wherein the bits which can be selected from the plurality of bits by means of the UE are permitted by a period-related parameter transferred by means of upper layer signaling.

TECHNICAL FIELD

Following description relates to a wireless communication system, andmore particularly, to a method for a V2X (vehicle to everything) UE(user equipment) to transmit control information and a message and anapparatus therefor.

BACKGROUND ART

Wireless communication systems have been widely deployed to providevarious types of communication services such as voice or data. Ingeneral, a wireless communication system is a multiple access systemthat supports communication of multiple users by sharing availablesystem resources (a bandwidth, transmission power, etc.) among them. Forexample, multiple access systems include a Code Division Multiple Access(CDMA) system, a Frequency Division Multiple Access (FDMA) system, aTime Division Multiple Access (TDMA) system, an Orthogonal FrequencyDivision Multiple Access (OFDMA) system, a Single Carrier FrequencyDivision Multiple Access (SC-FDMA) system, and a Multi-Carrier FrequencyDivision Multiple Access (MC-FDMA) system.

D2D communication is a communication scheme in which a direct link isestablished between User Equipments (UEs) and the UEs exchange voice anddata directly without an evolved Node B (eNB). D2D communication maycover UE-to-UE communication and peer-to-peer communication. Inaddition, D2D communication may be applied to Machine-to-Machine (M2M)communication and Machine Type Communication (MTC).

D2D communication is under consideration as a solution to the overheadof an eNB caused by rapidly increasing data traffic. For example, sincedevices exchange data directly with each other without an eNB by D2Dcommunication, compared to legacy wireless communication, networkoverhead may be reduced. Further, it is expected that the introductionof D2D communication will reduce procedures of an eNB, reduce the powerconsumption of devices participating in D2D communication, increase datatransmission rates, increase the accommodation capability of a network,distribute load, and extend cell coverage.

DISCLOSURE OF THE INVENTION Technical Task

A technical task of the present invention is to provide methods for aV2X UE to transmit control information and a message and various methodrelated to resource reservation.

Technical tasks obtainable from the present invention are non-limited bythe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, accordingto one embodiment, a method of transmitting data, which is transmittedby a UE in a wireless communication system, includes the steps oftransmitting a first message through time-frequency resources, andtransmitting the second message through a frequency resource regionidentical to a frequency resource region of the time-frequency resourcesafter prescribed time from the time-frequency resources, when it isnecessary for the UE to transmit a second message related to the firstmessage. In this case, the prescribed time is determined by a bitselected by the UE from among a plurality of bits and bits capable ofbeing selected by the UE from among a plurality of the bits can bepermitted by a period-related parameter forwarded via higher layersignaling.

The period-related parameter is transmitted from an F-node (fixed node)related to the UE and whether to permit the bits can be indicated by abitmap.

If the second message corresponds to a retransmission of the firstmessage, the second message can be transmitted within a retransmissioncount.

The retransmission count can be forwarded to the UE via higher layersignaling.

MCS within a range indicated by higher layer signaling can be used totransmit the first message.

The MCS can be used when speed of the UE is equal to or less than athreshold.

The speed equal to or less than the threshold can be forwarded viahigher layer signaling.

If the UE does not transmit the second message related to the firstmessage, the bit for determining the prescribed time can be selected by0.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, as embodied and broadly described,according to a different embodiment, a UE in a wireless communicationsystem includes a transmitter and a receiver, and a processor, theprocessor configured to transmit a first message through time-frequencyresources, the processor, if it is necessary for the UE to transmit asecond message related to the first message, configured to transmit thesecond message through a frequency resource region identical to afrequency resource region of the time-frequency resources afterprescribed time from the time-frequency resources. In this case, theprescribed time is determined by a bit selected by the UE from among aplurality of bits and bits capable of being selected by the UE fromamong a plurality of the bits can be permitted by a period-relatedparameter forwarded via higher layer signaling.

The period-related parameter is transmitted from an F-node (fixed node)related to the UE and whether to permit the bits can be indicated by abitmap.

If the second message corresponds to a retransmission of the firstmessage, the second message can be transmitted within a retransmissioncount.

The retransmission count can be forwarded to the UE via higher layersignaling.

MCS within a range indicated by higher layer signaling can be used totransmit the first message.

The MCS can be used when speed of the UE is equal to or less than athreshold.

The speed equal to or less than the threshold can be forwarded viahigher layer signaling.

Advantageous Effects

According to the present invention, a UE is able to transmit and receivea message in environment in which congestion control is appropriatelyperformed.

Effects obtainable from the present invention are non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a diagram for a structure of a radio frame;

FIG. 2 is a diagram for a resource grid in a downlink slot;

FIG. 3 is a diagram for a structure of a downlink subframe;

FIG. 4 is a diagram for a structure of an uplink subframe;

FIG. 5 is a diagram for a configuration of a wireless communicationsystem having multiple antennas;

FIG. 6 is a diagram for a subframe in which a D2D synchronization signalis transmitted;

FIG. 7 is a diagram for explaining relay of a D2D signal;

FIG. 8 is a diagram for an example of a D2D resource pool for performingD2D communication;

FIG. 9 is a diagram for explaining an SA period;

FIG. 10 is a diagram for explaining DCC (distributed congestioncontrol);

FIG. 11 is a flowchart for explaining one embodiment of the presentinvention;

FIG. 12 is a diagram for configurations of a transmitter and a receiver.

BEST MODE Mode for Invention

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions or features ofany one embodiment may be included in another embodiment and may bereplaced with corresponding constructions or features of anotherembodiment.

In the embodiments of the present invention, a description is made,centering on a data transmission and reception relationship between aBase Station (BS) and a User

Equipment (UE). The BS is a terminal node of a network, whichcommunicates directly with a UE. In some cases, a specific operationdescribed as performed by the BS may be performed by an upper node ofthe BS.

Namely, it is apparent that, in a network comprised of a plurality ofnetwork nodes including a BS, various operations performed forcommunication with a UE may be performed by the BS or network nodesother than the BS. The term ‘BS’ may be replaced with the term ‘fixedstation’, ‘Node B’, ‘evolved Node B (eNode B or eNB)’, ‘Access Point(AP)’, etc. The term ‘relay’ may be replaced with the term ‘Relay Node(RN)’ or ‘Relay Station (RS)’. The term ‘terminal’ may be replaced withthe term ‘UE’, ‘Mobile Station (MS)’, ‘Mobile Subscriber Station (MSS)’,‘Subscriber Station (SS)’, etc.

The term “cell”, as used herein, may be applied to transmission andreception points such as a base station (eNB), sector, remote radio head(RRH) and relay, and may also be extensively used by a specifictransmission/reception point to distinguish between component carriers.

Specific terms used for the embodiments of the present invention areprovided to help the understanding of the present invention. Thesespecific terms may be replaced with other terms within the scope andspirit of the present invention.

In some cases, to prevent the concept of the present invention frombeing ambiguous, structures and apparatuses of the known art will beomitted, or will be shown in the form of a block diagram based on mainfunctions of each structure and apparatus. Also, wherever possible, thesame reference numbers will be used throughout the drawings and thespecification to refer to the same or like parts.

The embodiments of the present invention can be supported by standarddocuments disclosed for at least one of wireless access systems,Institute of Electrical and Electronics Engineers (IEEE) 802, 3rdGeneration Partnership Project (3GPP), 3GPP Long Term Evolution (3GPPLTE), LTE-Advanced (LTE-A), and 3GPP2. Steps or parts that are notdescribed to clarify the technical features of the present invention canbe supported by those documents. Further, all terms as set forth hereincan be explained by the standard documents.

Techniques described herein can be used in various wireless accesssystems such as Code Division Multiple Access (CDMA), Frequency DivisionMultiple Access (FDMA), Time Division Multiple Access (TDMA), OrthogonalFrequency Division Multiple Access (OFDMA), Single Carrier-FrequencyDivision Multiple Access (SC-FDMA), etc. CDMA may be implemented as aradio technology such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA may be implemented as a radio technology such as GlobalSystem for Mobile communications (GSM)/General Packet Radio Service(GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may beimplemented as a radio technology such as IEEE 802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE 802.20, Evolved-UTRA (E-UTRA) etc. UTRA is a partof Universal Mobile Telecommunications System (UMTS). 3GPP LTE is a partof Evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA fordownlink and SC-FDMA for uplink. LTE-A is an evolution of 3GPP LTE.WiMAX can be described by the IEEE 802.16e standard (WirelessMetropolitan Area Network (WirelessMAN)-OFDMA Reference System) and theIEEE 802.16m standard (WirelessMAN-OFDMA Advanced System). For clarity,this application focuses on the 3GPP LTE and LTE-A systems. However, thetechnical features of the present invention are not limited thereto.

LTE/LTE-A Resource Structure/Channel

With reference to FIG. 1, the structure of a radio frame will bedescribed below.

In a cellular Orthogonal Frequency Division Multiplexing (OFDM) wirelessPacket communication system, uplink and/or downlink data Packets aretransmitted in subframes. One subframe is defined as a predeterminedtime period including a plurality of OFDM symbols. The 3GPP LTE standardsupports a type-1 radio frame structure applicable to Frequency DivisionDuplex (FDD) and a type-2 radio frame structure applicable to TimeDivision Duplex (TDD).

FIG. 1(a) illustrates the type-1 radio frame structure. A downlink radioframe is divided into 10 subframes. Each subframe is further dividedinto two slots in the time domain. A unit time during which one subframeis transmitted is defined as a Transmission Time Interval (TTI). Forexample, one subframe may be 1 ms in duration and one slot may be 0.5 msin duration. A slot includes a plurality of OFDM symbols in the timedomain and a plurality of Resource Blocks (RBs) in the frequency domain.Because the 3GPP LTE system adopts OFDMA for downlink, an OFDM symbolrepresents one symbol period. An OFDM symbol may be referred to as anSC-FDMA symbol or symbol period. An RB is a resource allocation unitincluding a plurality of contiguous subcarriers in a slot.

The number of OFDM symbols in one slot may vary depending on a CyclicPrefix (CP) configuration. There are two types of CPs: extended CP andnormal CP. In the case of the normal CP, one slot includes 7 OFDMsymbols. In the case of the extended CP, the length of one OFDM symbolis increased and thus the number of OFDM symbols in a slot is smallerthan in the case of the normal CP. Thus when the extended CP is used,for example, 6 OFDM symbols may be included in one slot. If channelstate gets poor, for example, during fast movement of a UE, the extendedCP may be used to further decrease Inter-Symbol Interference (ISI).

In the case of the normal CP, one subframe includes 14 OFDM symbolsbecause one slot includes 7 OFDM symbols. The first two or three OFDMsymbols of each subframe may be allocated to a Physical Downlink ControlCHannel (PDCCH) and the other OFDM symbols may be allocated to aPhysical Downlink Shared Channel (PDSCH).

FIG. 1(b) illustrates the type-2 radio frame structure. A type-2 radioframe includes two half frames, each having 5 subframes, a DownlinkPilot Time Slot (DwPTS), a Guard Period (GP), and an Uplink Pilot TimeSlot (UpPTS). Each subframe is divided into two slots. The DwPTS is usedfor initial cell search, synchronization, or channel estimation at a UE.The UpPTS is used for channel estimation and acquisition of uplinktransmission synchronization to a UE at an eNB. The GP is a periodbetween an uplink and a downlink, which eliminates uplink interferencecaused by multipath delay of a downlink signal. One subframe includestwo slots irrespective of the type of a radio frame.

The above-described radio frame structures are purely exemplary and thusit is to be noted that the number of subframes in a radio frame, thenumber of slots in a subframe, or the number of symbols in a slot mayvary.

FIG. 2 illustrates the structure of a downlink resource grid for theduration of one downlink slot. A downlink slot includes 7 OFDM symbolsin the time domain and an RB includes 12 subcarriers in the frequencydomain, which does not limit the scope and spirit of the presentinvention. For example, a downlink slot may include 7 OFDM symbols inthe case of the normal CP, whereas a downlink slot may include 6 OFDMsymbols in the case of the extended CP. Each element of the resourcegrid is referred to as a Resource Element (RE). An RB includes 12×7 REs.The number of RBs in a downlink slot, NDL depends on a downlinktransmission bandwidth. An uplink slot may have the same structure as adownlink slot.

FIG. 3 illustrates the structure of a downlink subframe. Up to threeOFDM symbols at the start of the first slot in a downlink subframe areused for a control region to which control channels are allocated andthe other OFDM symbols of the downlink subframe are used for a dataregion to which a PDSCH is allocated. Downlink control channels used inthe 3GPP LTE system include a Physical Control Format Indicator CHannel(PCFICH), a Physical Downlink Control CHannel (PDCCH), and a PhysicalHybrid automatic repeat request (HARQ) Indicator CHannel (PHICH). ThePCFICH is located in the first OFDM symbol of a subframe, carryinginformation about the number of OFDM symbols used for transmission ofcontrol channels in the subframe. The PHICH delivers an HARQACKnowledgment/Negative ACKnowledgment (ACK/NACK) signal in response toan uplink transmission. Control information carried on the PDCCH iscalled Downlink Control Information (DCI). The DCI transports uplink ordownlink scheduling information, or uplink transmission power controlcommands for UE groups. The PDCCH delivers information about resourceallocation and a transport format for a Downlink Shared CHannel(DL-SCH), resource allocation information about an Uplink Shared CHannel(UL-SCH), paging information of a Paging CHannel (PCH), systeminformation on the DL-SCH, information about resource allocation for ahigher-layer control message such as a Random Access Responsetransmitted on the PDSCH, a set of transmission power control commandsfor individual UEs of a UE group, transmission power controlinformation, Voice Over Internet Protocol (VoIP) activation information,etc. A plurality of PDCCHs may be transmitted in the control region. AUE may monitor a plurality of PDCCHs. A PDCCH is formed by aggregatingone or more consecutive Control Channel Elements (CCEs). A CCE is alogical allocation unit used to provide a PDCCH at a coding rate basedon the state of a radio channel. A CCE includes a plurality of REgroups. The format of a PDCCH and the number of available bits for thePDCCH are determined according to the correlation between the number ofCCEs and a coding rate provided by the CCEs. An eNB determines the PDCCHformat according to DCI transmitted to a UE and adds a Cyclic RedundancyCheck (CRC) to control information. The CRC is masked by an Identifier(ID) known as a Radio Network Temporary Identifier (RNTI) according tothe owner or usage of the PDCCH. If the PDCCH is directed to a specificUE, its CRC may be masked by a cell-RNTI (C-RNTI) of the UE. If thePDCCH is for a paging message, the CRC of the PDCCH may be masked by aPaging Indicator Identifier (P-RNTI). If the PDCCH carries systeminformation, particularly, a System Information Block (SIB), its CRC maybe masked by a system information ID and a System Information RNTI(SI-RNTI). To indicate that the PDCCH carries a Random Access Responsein response to a Random Access Preamble transmitted by a UE, its CRC maybe masked by a Random Access-RNTI (RA-RNTI).

FIG. 4 illustrates the structure of an uplink subframe. An uplinksubframe may be divided into a control region and a data region in thefrequency domain. A Physical Uplink Control CHannel (PUCCH) carryinguplink control information is allocated to the control region and aPhysical Uplink Shared Channel (PUSCH) carrying user data is allocatedto the data region. To maintain the property of a single carrier, a UEdoes not transmit a PUSCH and a PUCCH simultaneously. A PUCCH for a UEis allocated to an RB pair in a subframe. The RBs of the RB pair occupydifferent subcarriers in two slots. Thus it is said that the RB pairallocated to the PUCCH is frequency-hopped over a slot boundary.

Reference Signals (RSs)

In a wireless communication system, a Packet is transmitted on a radiochannel. In view of the nature of the radio channel, the Packet may bedistorted during the transmission. To receive the signal successfully, areceiver should compensate for the distortion of the received signalusing channel information. Generally, to enable the receiver to acquirethe channel information, a transmitter transmits a signal known to boththe transmitter and the receiver and the receiver acquires knowledge ofchannel information based on the distortion of the signal received onthe radio channel. This signal is called a pilot signal or an RS.

In the case of data transmission and reception through multipleantennas, knowledge of channel states between Transmission (Tx) antennasand Reception (Rx) antennas is required for successful signal reception.Accordingly, an RS should be transmitted through each Tx antenna.

RSs may be divided into downlink RSs and uplink RSs. In the current LTEsystem, the uplink RSs include:

i) DeModulation-Reference Signal (DM-RS) used for channel estimation forcoherent demodulation of information delivered on a PUSCH and a PUCCH;and

ii) Sounding Reference Signal (SRS) used for an eNB or a network tomeasure the quality of an uplink channel in a different frequency.

The downlink RSs are categorized into:

i) Cell-specific Reference Signal (CRS) shared among all UEs of a cell;

ii) UE-specific RS dedicated to a specific UE;

iii) DM-RS used for coherent demodulation of a PDSCH, when the PDSCH istransmitted;

iv) Channel State Information-Reference Signal (CSI-RS) carrying CSI,when downlink DM-RSs are transmitted;

v) Multimedia Broadcast Single Frequency Network (MBSFN) RS used forcoherent demodulation of a signal transmitted in MBSFN mode; and

vi) positioning RS used to estimate geographical position informationabout a UE.

RSs may also be divided into two types according to their purposes: RSfor channel information acquisition and RS for data demodulation. Sinceits purpose lies in that a UE acquires downlink channel information, theformer should be transmitted in a broad band and received even by a UEthat does not receive downlink data in a specific subframe. This RS isalso used in a situation like handover. The latter is an RS that an eNBtransmits along with downlink data in specific resources. A UE candemodulate the data by measuring a channel using the RS. This RS shouldbe transmitted in a data transmission area.

Modeling of MIMO System

FIG. 5 is a diagram illustrating a configuration of a wirelesscommunication system having multiple antennas.

As shown in FIG. 5(a), if the number of transmit antennas is increasedto NT and the number of receive antennas is increased to NR, atheoretical channel transmission capacity is increased in proportion tothe number of antennas, unlike the case where a plurality of antennas isused in only a transmitter or a receiver. Accordingly, it is possible toimprove a transfer rate and to remarkably improve frequency efficiency.As the channel transmission capacity is increased, the transfer rate maybe theoretically increased by a product of a maximum transfer rate Roupon utilization of a single antenna and a rate increase ratio Ri.

R _(i)=min(N _(T) , N _(R))   [Equation 1 ]

For instance, in an MIMO communication system, which uses 4 transmitantennas and 4 receive antennas, a transmission rate 4 times higher thanthat of a single antenna system can be obtained. Since this theoreticalcapacity increase of the MIMO system has been proved in the middle of90′s, many ongoing efforts are made to various techniques tosubstantially improve a data transmission rate. In addition, thesetechniques are already adopted in part as standards for various wirelesscommunications such as 3G mobile communication, next generation wirelessLAN and the like.

The trends for the MIMO relevant studies are explained as follows. Firstof all, many ongoing efforts are made in various aspects to develop andresearch information theory study relevant to MIMO communicationcapacity calculations and the like in various channel configurations andmultiple access environments, radio channel measurement and modelderivation study for MIMO systems, spatiotemporal signal processingtechnique study for transmission reliability enhancement andtransmission rate improvement and the like.

In order to explain a communicating method in an MIMO system in detail,mathematical modeling can be represented as follows. It is assumed thatthere are NT transmit antennas and NR receive antennas.

Regarding a transmitted signal, if there are NT transmit antennas, themaximum number of pieces of information that can be transmitted is NT.Hence, the transmission information can be represented as shown inEquation 2.

s=, [s₁, s₂, . . . , s_(N) _(T) ]^(T)   [Equation 2]

Meanwhile, transmit powers can be set different from each other forindividual pieces of transmission information s₁, s₂, . . . , s_(N)T,respectively. If the transmit powers are set to P₁, P₂, . . . , P_(N)_(t) , respectively, the transmission information with adjusted transmitpowers can be represented as Equation 3.

ŝ=[ŝ₁, ŝ₂, . . . , ŝ_(N) _(T) ]^(T) =[P ₁ s ₁ , P ₂ s ₂ , . . . ,P _(n)_(T) s _(n) _(T) ]^(T)   [Equation 3]

In addition, Ŝ can be represented as Equation 4 using diagonal matrix Pof the transmission power.

$\begin{matrix}{\hat{s} = {{\begin{bmatrix}P_{1} & \; & \; & 0 \\\; & P_{2} & \; & \; \\\; & \; & \ddots & \; \\0 & \; & \; & P_{N_{T}}\end{bmatrix}\begin{bmatrix}s_{1} \\s_{2} \\\vdots \\s_{N_{T}}\end{bmatrix}} = {Ps}}} & \lbrack {{Equation}\mspace{14mu} 4} \rbrack\end{matrix}$

Assuming a case of configuring NT transmitted signals x₁, x₂, . . . ,x_(N) _(T) , which are actually transmitted, by applying weight matrix Wto the information vector Ŝ having the adjusted transmit powers, theweight matrix W serves to appropriately distribute the transmissioninformation to each antenna according to a transport channel state. x₁,x₂, . . . , x_(N) _(T) can expresse by using the vector X as follows.

$\begin{matrix}{x = {\quad{\begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{i} \\\vdots \\x_{N_{T}}\end{bmatrix} = {{\begin{bmatrix}w_{11} & w_{12} & \ldots & w_{1N_{T}} \\w_{21} & w_{22} & \ldots & w_{2N_{T}} \\\vdots & \; & \ddots & \; \\w_{i\; 1} & w_{i\; 2} & \ldots & w_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\w_{N_{T}1} & w_{N_{T}2} & \ldots & w_{N_{T}N_{T}}\end{bmatrix}\begin{bmatrix}{\hat{s}}_{1} \\{\hat{s}}_{2} \\\vdots \\{\hat{s}}_{j} \\\vdots \\{\hat{s}}_{N_{T}}\end{bmatrix}} = {{W\hat{s}} = {WPs}}}}}} & \lbrack {{Equation}\mspace{14mu} 5} \rbrack\end{matrix}$

In Equation 5, w_(ij) denotes a weight between an i^(th) transmitantenna and j^(th) information. W is also called a precoding matrix.

If the NR receive antennas are present, respective received signals y₁,y₂, . . . , y_(N) _(R) of the antennas can be expressed as follows.

y=[y₁, y₂, . . . , y_(N) _(R) ]^(T)   [Equation 6]

If channels are modeled in the MIMO wireless communication system, thechannels may be distinguished according to transmit/receive antennaindexes. A channel from the transmit antenna j to the receive antenna iis denoted by h_(ij) . In, h_(ij), it is noted that the indexes of thereceive antennas precede the indexes of the transmit antennas in view ofthe order of indexes.

FIG. 5(b) is a diagram illustrating channels from the NT transmitantennas to the receive antenna i. The channels may be combined andexpressed in the form of a vector and a matrix. In FIG. 5(b), thechannels from the NT transmit antennas to the receive antenna i can beexpressed as follows.

h_(i) ^(T)=[h_(i1), h_(i2), . . . , h_(iN) _(T) ]  [Equation 7]

Accordingly, all channels from the NT transmit antennas to the NRreceive antennas can be expressed as follows.

$\begin{matrix}{H = {\begin{bmatrix}h_{1}^{T} \\h_{2}^{T} \\\vdots \\h_{i}^{T} \\\vdots \\h_{N_{R}}^{T}\end{bmatrix} = \begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1N_{T}} \\h_{21} & h_{22} & \ldots & h_{2N_{T}} \\\vdots & \; & \ddots & \; \\h_{i\; 1} & h_{i\; 2} & \ldots & h_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\h_{N_{R}1} & h_{N_{R}2} & \ldots & h_{N_{R}N_{T}}\end{bmatrix}}} & \lbrack {{Equation}\mspace{14mu} 8} \rbrack\end{matrix}$

An AWGN (Additive White Gaussian Noise) is added to the actual channelsafter a channel matrix H. The AWGN n₁, n₂, . . . , n_(N) _(R)respectively added to the NR receive antennas can be expressed asfollows.

n=[n₁, n₂, . . . , n_(N) _(R) ]^(T)   [Equation 9]

Through the above-described mathematical modeling, the received signalscan be expressed as follows.

$\begin{matrix}{y = {\quad{\begin{bmatrix}y_{1} \\y_{2} \\\vdots \\y_{i} \\\vdots \\y_{N_{R}}\end{bmatrix} = {{{\begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1N_{T}} \\h_{21} & h_{22} & \ldots & h_{2N_{T}} \\\vdots & \; & \ddots & \; \\h_{i\; 1} & h_{i\; 2} & \ldots & h_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\h_{N_{R}1} & h_{N_{R}2} & \ldots & h_{N_{R}N_{T}}\end{bmatrix}\begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{j} \\\vdots \\x_{N_{T}}\end{bmatrix}} + \begin{bmatrix}n_{1} \\n_{2} \\\vdots \\n_{i} \\\vdots \\n_{N_{R}}\end{bmatrix}} = {{Hx} + n}}}}} & \lbrack {{Equation}\mspace{14mu} 10} \rbrack\end{matrix}$

Meanwhile, the number of rows and columns of the channel matrix Hindicating the channel state is determined by the number of transmit andreceive antennas. The number of rows of the channel matrix H is equal tothe number NR of receive antennas and the number of columns thereof isequal to the number NR of transmit antennas. That is, the channel matrixH is an NRxNT matrix.

The rank of the matrix is defined by the smaller of the number of rowsand the number of columns, which are independent from each other.Accordingly, the rank of the matrix is not greater than the number ofrows or columns. The rank rank(H) of the channel matrix ii is restrictedas follows.

rank(H)≤min(N _(T) , N _(R))   [Equation 11]

Additionally, the rank of a matrix can also be defined as the number ofnon-zero Eigen values when the matrix is Eigen-value-decomposed.Similarly, the rank of a matrix can be defined as the number of non-zerosingular values when the matrix is singular-value-decomposed.Accordingly, the physical meaning of the rank of a channel matrix can bethe maximum number of channels through which different pieces ofinformation can be transmitted.

In the description of the present document, ‘rank’ for MIMO transmissionindicates the number of paths capable of sending signals independentlyon specific time and frequency resources and ‘number of layers’indicates the number of signal streams transmitted through therespective paths. Generally, since a transmitting end transmits thenumber of layers corresponding to the rank number, one rank has the samemeaning of the layer number unless mentioned specially.

Synchronization Acquisition of D2D UE

Now, a description will be given of synchronization acquisition betweenUEs in D2D communication based on the foregoing description in thecontext of the legacy LTE/LTE-A system. In an OFDM system, iftime/frequency synchronization is not acquired, the resulting Inter-CellInterference (ICI) may make it impossible to multiplex different UEs inan OFDM signal. If each individual D2D UE acquires synchronization bytransmitting and receiving a synchronization signal directly, this isinefficient. In a distributed node system such as a D2D communicationsystem, therefore, a specific node may transmit a representativesynchronization signal and the other UEs may acquire synchronizationusing the representative synchronization signal. In other words, somenodes (which may be an eNB, a UE, and a Synchronization Reference Node(SRN, also referred to as a synchronization source)) may transmit a D2DSynchronization Signal (D2DSS) and the remaining UEs may transmit andreceive signals in synchronization with the D2DSS.

D2DSSs may include a Primary D2DSS (PD2DSS) or a Primary SidelinkSynchronization Signal (PSSS) and a Secondary D2DSS (SD2DSS) or aSecondary Sidelink Synchronization Signal (SSSS). The PD2DSS may beconfigured to have a similar/modified/repeated structure of a Zadoff-chusequence of a predetermined length or a Primary Synchronization Signal(PSS). Unlike a DL PSS, the PD2DSS may use a different Zadoff-chu rootindex (e.g., 26, 37). And, the SD2DSS may be configured to have asimilar/modified/repeated structure of an M-sequence or a SecondarySynchronization Signal (SSS). If UEs synchronize their timing with aneNB, the eNB serves as an SRN and the D2DSS is a PSS/SSS. Unlike PSS/SSSof DL, the PD2DSS/SD2DSS follows UL subcarrier mapping scheme. FIG. 6shows a subframe in which a D2D synchronization signal is transmitted. APhysical D2D Synchronization Channel (PD2DSCH) may be a (broadcast)channel carrying basic (system) information that a UE should firstobtain before D2D signal transmission and reception (e.g., D2DSS-relatedinformation, a Duplex Mode (DM), a TDD UL/DL configuration, a resourcepool-related information, the type of an application related to theD2DSS, etc.). The PD2DSCH may be transmitted in the same subframe as theD2DSS or in a subframe subsequent to the frame carrying the D2DSS. ADMRS can be used to demodulate the PD2DSCH.

The SRN may be a node that transmits a D2DSS and a PD2DSCH. The D2DSSmay be a specific sequence and the PD2DSCH may be a sequencerepresenting specific information or a codeword produced bypredetermined channel coding. The SRN may be an eNB or a specific D2DUE. In the case of partial network coverage or out of network coverage,the SRN may be a UE.

In a situation illustrated in FIG. 7, a D2DSS may be relayed for D2Dcommunication with an out-of-coverage UE. The D2DSS may be relayed overmultiple hops. The following description is given with the appreciationthat relay of an SS covers transmission of a D2DSS in a separate formataccording to a SS reception time as well as direct Amplify-and-Forward(AF)-relay of an SS transmitted by an eNB. As the D2DSS is relayed, anin-coverage UE may communicate directly with an out-of-coverage UE.

D2D Resource Pool

FIG. 8 shows an example of a UE1, a UE2 and a resource pool used by theUE1 and the UE2 performing D2D communication. In FIG. 8(a), a UEcorresponds to a terminal or such a network device as an eNBtransmitting and receiving a signal according to a D2D communicationscheme. A UE selects a resource unit corresponding to a specificresource from a resource pool corresponding to a set of resources andthe UE transmits a D2D signal using the selected resource unit. A UE2corresponding to a reception UE receives a configuration of a resourcepool in which the UE1 is able to transmit a signal and detects a signalof the UE1 in the resource pool. In this case, if the UE1 is located atthe inside of coverage of an eNB, the eNB can inform the UE1 of theresource pool. If the UE1 is located at the outside of coverage of theeNB, the resource pool can be informed by a different UE or can bedetermined by a predetermined resource. In general, a resource poolincludes a plurality of resource units. A UE selects one or moreresource units from among a plurality of the resource units and may beable to use the selected resource unit(s) for D2D signal transmission.FIG. 8(b) shows an example of configuring a resource unit. Referring toFIG. 8 (b), the entire frequency resources are divided into the N_(F)number of resource units and the entire time resources are divided intothe N_(T) number of resource units. In particular, it is able to defineN_(F)*N_(T) number of resource units in total. In particular, a resourcepool can be repeated with a period of N_(T) subframes. Specifically, asshown in FIG. 8, one resource unit may periodically and repeatedlyappear. Or, an index of a physical resource unit to which a logicalresource unit is mapped may change with a predetermined patternaccording to time to obtain a diversity gain in time domain and/orfrequency domain. In this resource unit structure, a resource pool maycorrespond to a set of resource units capable of being used by a UEintending to transmit a D2D signal.

A resource pool can be classified into various types. First of all, theresource pool can be classified according to contents of a D2D signaltransmitted via each resource pool. For example, the contents of the D2Dsignal can be classified into various signals and a separate resourcepool can be configured according to each of the contents. The contentsof the D2D signal may include SA (scheduling assignment), a D2D datachannel, and a discovery channel. The SA may correspond to a signalincluding information on a resource position of a D2D data channel,information on MCS (modulation and coding scheme) necessary formodulating and demodulating a data channel, information on a MIMOtransmission scheme, information on TA (timing advance), and the like.The SA signal can be transmitted on an identical resource unit in amanner of being multiplexed with D2D data. In this case, an SA resourcepool may correspond to a pool of resources that an SA and D2D data aretransmitted in a manner of being multiplexed. The SA signal can also bereferred to as a D2D control channel or a PSCCH (physical sidelinkcontrol channel). The D2D data channel (or, PSSCH (physical sidelinkshared channel)) corresponds to a resource pool used by a transmissionUE to transmit user data. If an SA and a D2D data are transmitted in amanner of being multiplexed in an identical resource unit, D2D datachannel except SA information can be transmitted only in a resource poolfor the D2D data channel. In other word, resource elements (REs), whichare used to transmit SA information in a specific resource unit of an SAresource pool, can also be used for transmitting D2D data in a D2D datachannel resource pool. The discovery channel may correspond to aresource pool for a message that enables a neighboring UE to discovertransmission UE transmitting information such as ID of the UE, and thelike.

Although contents of D2D signal are identical to each other, it may usea different resource pool according to a transmission/receptionattribute of the D2D signal. For example, in case of the same D2D datachannel or the same discovery message, the D2D data channel or thediscovery signal can be classified into a different resource poolaccording to a transmission timing determination scheme (e.g., whether aD2D signal is transmitted at the

Docket No. 2101-71386 time of receiving a synchronization referencesignal or the timing to which a prescribed timing advance is added) of aD2D signal, a resource allocation scheme (e.g., whether a transmissionresource of an individual signal is designated by an eNB or anindividual transmission UE selects an individual signal transmissionresource from a pool), a signal format (e.g., number of symbols occupiedby a D2D signal in a subframe, number of subframes used for transmittinga D2D signal), signal strength from an eNB, strength of transmit powerof a D2D UE, and the like. For clarity, a method for an eNB to directlydesignate a transmission resource of a D2D transmission UE is referredto as a mode 1. If a transmission resource region is configured inadvance or an eNB designates the transmission resource region and a UEdirectly selects a transmission resource from the transmission resourceregion, it is referred to as a mode 2. In case of performing D2Ddiscovery, if an eNB directly indicates a resource, it is referred to asa type 2. If a UE directly selects a transmission resource from apredetermined resource region or a resource region indicated by the eNB,it is referred to as a type 1.

Transmission and Reception of SA

A mode 1 UE can transmit an SA signal (or, a D2D control signal, SCI(sidelink control information)) via a resource configured by an eNB. Amode 2 UE receives a configured resource to be used for D2Dtransmission. The mode 2 UE can transmit SA by selecting a timefrequency resource from the configured resource.

The SA period can be defined as FIG. 9. Referring to FIG. 9, a first SAperiod can start at a subframe apart from a specific system frame asmuch as a prescribed offset (SAOffsetlndicator) indicated by higherlayer signaling. Each SA period can include an SA resource pool and asubframe pool for transmitting D2D data. The SA resource pool caninclude subframes ranging from a first subframe of an SA period to thelast subframe among subframes indicated by a subframe bitmap(saSubframeBitmap) to transmit SA. In case of mode 1, T-RPT(time-resource pattern for transmission) is applied to the resource poolfor transmitting D2D data to determine a subframe in which an actualdata is transmitted. As shown in the drawing, if the number of subframesincluded in an SA period except the SA resource pool is greater than thenumber of T-RPT bits, the T-RPT can be repeatedly applied and the lastlyapplied T-RPT can be applied in a manner of being truncated as many asthe number of remaining subframes. A transmission UE performstransmission at a position where a T-RPT bitmap corresponds to 1 in anindicated T-RPT and 4 transmissions are performed in a MAC PDU.

FIG. 10 illustrates an operation scheme for DCC (distributed congestioncontrol) defined in 802.11p. When a CBP (channel busy percentage) ismeasured by a UE, if load is equal to or greater than a certain level,the DCC changes a state (relaxed, active, restrictive). When the stateis changed, not only Tx power but also Phy. rate, a sensing threshold,and a message transmission frequency are changed at the same time. And,inter message reception time is considerably changed according to thechange of the state. When a state is changed, since too many parametersare changed at the same time, the DCC has a demerit in that it isdifficult to identify a parameter that affects performance. When the DCCis performed, since congestion measurement (Occupation energy of achannel is measured for prescribed time. If the energy is equal to orgreater than a threshold/upper limit, it is determined that the channelis in a busy state. If busy percentage is equal to or greater than athreshold or is equal to or less than the threshold in a specific timewindow, a state is changed) is performed by a UE, a congestiondiscordance phenomenon may occur between UEs. For example, when a UEgroup A determines a channel as busy and reduces channel access, a UEgroup B adjacent to the UE group A may determine that the channel isidle because the channel is not used by the UE group A and may have ahigh channel access parameter. In this case, a performance inequalityphenomenon (a specific UE group continuously uses an active state,whereas a different specific UE group continuously uses a restrictivestate) may occur between the UE group A and the UE group B. Or, a UElocated at a specific region may switch a state between an active stateand a restrictive state (or, between a relaxed state and an activestate).

In the following, a method of solving the demerits (the congestionmeasurement of the UE, the performance inequality phenomenon, and thelike) of the DCC and a method of controlling interference in anovercrowded region in V2X communication are described. Terminologiesused in the following description are explained.

F-node: a device for controlling V2X communication at a fixed positionor a device for providing help is referred to as a fixed node. TheF-node may have a form of an eNB or a UE type. The F-node can also bereferred to as an RSU (road side unit).

V-UE: a terminal mounted on a moving vehicle or a UE used by a driver ofa moving vehicle is referred to as a V-UE.

P-UE: a terminal held by a person moving on a street is referred to as apedestrian UE (P-UE). A person may move using a bicycle or a differentmoving means (Segway, electric wheel). In general, the P-UE correspondsto a terminal having mobility lower than that of the V-UE.

A UE may operate with a different behavior when all or a part ofparameters i) to vii) is different.

i) MCS: modulation and coding or RB size

ii) Tx power: Tx power of a terminal

iii) Message generation period: A period of transmitting a messagetransmitted by a terminal (Or, a period of reserving a message. It maycorrespond to a period of reserving a resource when a terminal uses semipersistent transmission. In the following, unless there is a separateexplanation, the message generation period includes an SPS period.)

iv) Repetition number: The number of retransmitting a single MAC PDUretransmitted by a terminal.

v) Sensing threshold/limit: When a terminal determines whether a channelis idle or busy, such a threshold/limit as RSSI or RSRP. Specifically,the threshold/limit may be associated with a sensing method. Whensensing is performed, if a measurement value measured by a terminal ishigher than the threshold/limit, the terminal determines that a channelis busy. Otherwise, the terminal determines that a channel is idle.

vi) Contention window (CW) size: If a terminal knows that a channel isempty in advance via other information or determines that the channel isidle, the terminal can decrease a backoff counter by 1 in a contentionwindow. In other word, the counter is initially configured by a CW sizeand is decreased by 1 whenever a channel is idle. If the counter becomes0, transmission is performed.

vii) Resource pool: A resource pool can be differently used according toa type of a UE, a message type, or geo-information (location, speed,orientation, etc.) of a UE.

UE Behavior Signaling of F-Node

An F-node signals a common measurement value and/or a UE behavior (allor a part of an MCS/MCS range, Tx power, a message generation period, arepetition number (range), a sensing threshold, and a contention size)to a V-UE via physical layer signaling or higher layer signaling and canmake the V-UE, which has received the common measurement value and/orthe UE behavior, operate according to the behavior indicated by theF-node. The UE behavior can be differently designated depending on aregion. For example, a resource pool or a set of resources usable in theresource pool can be differently configured according to geo locationinformation (location, speed, orientation, etc.) of a UE. In this case,the F-node can signal a UE behavior used in each of resource regions (aresource pool, a resource set, a resource subset in a resource pool) toa UE via physical layer signaling or higher layer signaling. If there isno F-node near a UE, a UE behavior (e.g., MCS, RB size, etc.) capable ofbeing used according to a resource pool can be determined in advance.

The UE behavior signaled by the F-node can be determined based onmeasurement values measured by V-UEs. More specifically, a V-UE cansignal a status (or, UE behavior) determined according to a measurementvalue and/or measurement to the F-node via physical layer signaling orhigher layer signaling. The F-node can calculate a common measurementvalue of a corresponding region based on a status or a measurement valuereceived from a nearby UE. The F-node can determine a UE behavior basedon the calculated common measurement value and signal the determined UEbehavior to a V-UE. The F-node can signals an average of measurementvalues received from a UE rather than the UE behavior to a V-UE viaphysical layer signaling or higher layer signaling. In order to set acommon behavior among F-nodes, it may share a measurement value and/orall or a part of UE behavior-related parameters (MCS, Tx power, amessage generation period (or SPS period), repetition (retransmission)number, a sensing threshold, and a contention window size) via abackhaul or a radio channel between F-nodes.

The F-node can designate a specific MCS scheme to be used by a UE. Or,the F-node can designate a range of an MCS usable in a correspondingregion. In this case, as mentioned in the foregoing description, the MCSor the range of the MCS can be used by specific geo location information(location, speed, orientation, etc.) and/or a resource pool. Forexample, an MCS range used by a UE at a speed equal to or less than athreshold/limit can be signaled via higher layer signaling. If there isno F-node near a UE, a UE behavior (e.g., MCS, RB size, etc.) capable ofbeing used according to a resource pool can be determined in advance.When a UE moves fast, this scheme can be usefully used for configuringMCS to be lower in consideration of a relative speed with a receptionUE. If a UE autonomously determines MCS according to speed, the UEdetermines the MCS without considering relative speed with a receptionUE. In this case, since F-nodes are able to know average relative speedbetween UEs in a corresponding region, if the F-nodes determines MCS oran MCS range optimized for transmission and reception of the UEs,transmission/reception performance between the UEs can be enhanced.

The F-node can forward information on a threshold/limit speed (range) tobe used for an RRC-signaled UE behavior to a UE via higher layersignaling. In this case, the UE can use/apply UE behavior-relatedparameters (MCS/MCS range, Tx power, message generation period,repetition number (range), sensing threshold, contention window size)signaled via RRC signaling within an RRC-signaled speed range. Or, whenspeed of UEs is equal to or greater than a prescribed level, all or apart of Tx power of the UEs, MCS RB size, and the like can be signaledto a UE. More generally, a network (F-node) can signal a condition forwhich a UE configures a transmission parameter or an upper limit and/ora lower limit of a transmission parameter to a UE via physical layersignaling or higher layer signaling. In this case, each condition maycorrespond to geo location information of a UE, speed, load of aresource region (a ratio of occupied resources to resources belonging toa specific resource region), and the like.

Meanwhile, a behavior value of a different UE can be signaled dependingon a message size or a priority. For example, it may be able toconfigure an event triggered message to more frequently and more quicklytransmit a signal by setting a repetition value or a sensingthreshold/limit value higher than that of a periodic message to theevent triggered message. Among periodic messages, if a message istransmitted with a long interval (the message of the long interval caninclude security information on a message of a short interval and thelike), the message transmitted with the long interval can be configuredby a different UE behavior compared to a message transmitted with ashort interval.

When a UE changes a UE behavior according to the aforementioned geolocation information of the UE, the UE may change not only MCS and RBsize but also transmit power.

Meanwhile, when a UE transmits feedback information to an F-node, aratio of occupied resources to resources belonging to a specificresource region can be included in the feedback information. In thiscase, the ratio of the occupied resources to the resources belonging tothe specific resource region can be calculated by three methodsdescribed in the following. A first method corresponds to a based on SAdecoding method. A data resource associated with SA can be known via SAdecoding. A UE can calculate a ratio of occupied resources in the entiredata resource region. A second method corresponds to an energy sensingmethod. If energy (RSSI or RSRP (of an RS)) measured at a specificresource unit exceeds a prescribed threshold, it may consider it as acorresponding resource is occupied. A UE can calculate a ratio ofoccupied resources in the entire data resource region. A third methodcorresponds to a method based on both SA decoding and energy sensing. Itmay be able to signal all or a part of an average energy amount measuredat a specific resource region, average RSSI/RSRP/RSRQ between D2D UEs, aratio of dropped packets, and an average decoding success/failure ratein a specific resource region via physical layer signaling or higherlayer signaling. In this case, separate information can be signaled as atransmission mode (mode 1 or mode 2) of a UE according to a resourceregion. To this end, an F-node can indicate a D2D UE to report ameasurement result measured at a specific resource region via physicallayer signaling or higher layer signaling. All or a part of D2D UEs cansignal measurement information to the F-node (with a predetermined rate,a rate indicated by a network, a predetermined interval, or an intervalindicated by the network) via physical layer signaling or higher layersignaling. F-nodes collect the information and may utilize theinformation for such an operation as configuration of a transmissionparameter of a UE, reconfiguration of a resource region, change betweenMode 1/Mode 2, and the like. And, the information can be directlyutilized by the UE. The UE may refer to the information for configuringa transmission parameter of the UE (all or a part of transmit power,resource size (RB size, retransmission count), MCS, and the like). Ifthe UE is indicated to report the information, the UE can periodicallyor aperiodically report the information via physical layer signaling orhigher layer signaling.

Meanwhile, if there is no F-node, parameters of a UE behavior can bedetermined in advance. In this case, it may use a different contentionparameter depending on a message type. For example, it may use adifferent parameter according to a priority of a message. The priorityof the message can be determined in an order of Event triggeredmessage>Periodic message with security information>periodic messagewithout security information. A priority according to a message can bedetermined by a higher layer. In this case, the event triggered messagecorresponds to a message which is transmitted when a specific eventoccurs. An accident, danger, and the like can be notified via the eventtriggered message. The periodic message with security information (or, along period periodic message) may correspond to a periodic messagetransmitted with a relatively long period and may have securityinformation of a message transmitted with a short period. The periodicmessage without security information (or, a short period periodicmessage) may correspond to a periodic message transmitted with arelatively short period and may correspond to a frequently transmittedmessage after the long period message. For example, if a message has ahigher priority, it may configure a repetition number to be bigger tomake the message have higher access probability (A CW can be configuredto be smaller than a message of a low priority. Or, a sensingthreshold/limit is configured to be higher. (More specifically, a UEcompares a priority of a message to be transmitted by the UE with apriority of a message occupying a resource. If the priority of themessage to be transmitted by the UE is higher, a higher sensingthreshold is set to the message to make the UE have an opportunity ofusing the resource. To this end, an F-node can signal a sensingthreshold according to a priority to the UE via physical layer signalingor higher layer signaling.)) All or a part of parameters (MCS/MCS range,Tx power, message generation period, repetition number (range), sensingthreshold, contention window size) can be differently configuredaccording to a priority. When a parameter is configured according to apriority, the priority can be determined in advance according to amessage type or contents.

UE Behavior Signaling of UE

UEs (or V-UEs) can transmit all or a part of parameters for measuring ordetermining behaviors of the UEs in a manner of including the parametersin a control signal which is transmitted or piggy backed together withSA (control signal), a MAC header (or, MAC CE or a different higherlayer field) of data, or data. In this case, a behavior or a measurementcan be shared between UEs without an F-node and it may refer to thebehavior to determine a behavior of the UE. All or a part of parametersincluding MCS, Tx power, Message generation period, Repetition number,Sensing threshold, Contention window size and the like can be includedin a MAC header (or, MAC CE or a different higher layer field) of a UEor SA. For example, if MCS, message generation period, Tx power, CWsize, a threshold/limit are transmitted in a manner of being included inthe SA or the MAC header (or, MAC CE or a different higher layer field),a UE can determine a behavior of the UE in consideration of behaviors ofnearby UEs.

Among the aforementioned UE behavior signal of a UE, a messagegeneration period may correspond to semi persistent scheduling formaintaining a current resource allocation after X ms. In particular, thecurrent resource allocation can be maintained after X ms according to avalue of the message generation period. An SPS period value can betransmitted in a manner of being included in SA. An SA period (or, amessage generation period) interval or the number of SA periods can betransmitted in a manner of being included in SA to indicate the numberof SA periods during which a current resource allocation is to bemaintained in the future.

Specifically, a UE selects an information bit related to resourcereservation to be included in control information and can transmit thecontrol information via a channel on which the control information isforwarded. In this case, the information bit can indicate whether or notthe UE reserves a resource. If the UE reserves a resource, theinformation bit can also indicate a position of the resource. Inparticular, a method of indicating a length of a period for indicatingreservation of a resource in a next transmission and a method ofindicating whether or not reservation is made in a next period can beimplemented in a manner of being combined. For example, if a UE does notreserve a resource, 0 is selected as a value of the information bit. Ifa UE reserves a resource, a value rather than 0 is selected as the valueof the information bit. The UE can transmit data after a time periodcorresponding to the value rather than 0 is elapsed. As a differentexample, 2-bit state can be transmitted in a manner of being included inSA. In this case, a bit state 00 indicates that reservation is notperformed. Bit states 01, 10, and 11 may indicate an SPS period length.As a further different example, a UE can configure an SPS period rangingfrom 100 ms to 1000 ms. In this case, a field of 4 bits can betransmitted in a manner of being included in SA. In this case, 00 mayindicate that a resource is not reserved in a next period.

Referring to FIG. 11, a reception UE receives control information via achannel on which the control information is forwarded [S1101] and cancheck an information bit related to resource reservation included in thecontrol information. As mentioned in the foregoing description, theinformation bit can indicate whether or not the UE reserves a resource.If the UE reserves a resource, the information bit can also indicate aposition of the resource. Hence, the reception UE can determine whetheror not a value of the information bit related to resource reservationcorresponds to 0 [S1102]. If the information bit corresponds to 0, theUE can anticipate/assume/premise that the UE, which has transmitted thecontrol information, does not reserve a resource [S1103]. If theinformation bit corresponds to a value rather than 0, the UE cananticipate/assume/premise that the UE, which has transmitted the controlinformation, reserves the same frequency resource after a time periodcorresponding to the information bit and transmits data after the timeperiod corresponding to the information bit [S1104]. In this case, ifthe UE corresponds to a UE receiving data corresponding to the controlinformation, the UE can decode the data in a frequency resourceidentical to a resource in which the data is received after the timeperiod. If the UE corresponds to a UE not receiving data correspondingto the control information, the UE can exclude a frequency resource inwhich the data is received after the time period when the UE selects atransmission resource.

In the foregoing description, a value selected as an information bit maycorrespond to a value permitted by a period-related parameter which isforwarded by an F-node via higher layer signaling. In particular, when aUE transmits data, the UE selects an information bit related to resourcereservation according to UE behavior signaling of the F-node. Morespecifically, a first message can be transmitted via a time-frequencyresource. If it is necessary for a UE to transmit a second messagerelated to the first message, the UE can transmit the second message viaa frequency resource region identical to a frequency resource regionamong the time-frequency resource after prescribed time is elapsed fromthe time-frequency resource. In this case, the prescribed time isdetermined by a bit (the information bit related to resourcereservation) selected by the UE from among a plurality of bits. Bitscapable of being selected by the UE from among a plurality of the bitscan be permitted by a period-related parameter forwarded via higherlayer signaling. Whether to permit the bits can be indicated by a bitmapvia higher layer signaling. For example, it may signal usable periodinformation among 10 states including 100, 200, . . . , 1000 to a UE ina bitmap form. For example, a bitmap 1010101010 may indicate that a UEis able to use such a period as 100, 300, 500, 700, and 900 only. Theperiod-related parameter can be transmitted from an F-node (fixed node)related to a UE. In particular, resource reservation can beappropriately controlled by the F-node. In this case, it may preventsuch an operation that a UE indiscreetly reserves a resource appearingafter long time. As an extreme case, the F-node can always configure aspecific period (e.g., 100 ms) as an SPS period only used by UEs. Inthis case, the F-node configures all UEs to transmit a message with thespecific period.

Besides the selection of the information bit related to resourcereservation, UE behavior signaling of the F-node can control variousoperations of a UE described in the following. For example, if a secondmessage corresponds to a retransmission of a first message, the secondmessage can be transmitted within a retransmission count. In this case,the retransmission count can be forwarded to a UE via higher layersignaling. When the first message is transmitted, it may use MCS withina range indicated by higher layer signaling. The MCS can be used when aUE is within speed equal to or less than threshold speed or a specificspeed range. The speed equal to or less than the threshold speed or thespecific speed range can be forwarded via higher layer signaling.

A resource for control information and a resource for data correspondingto the control information can be selected at the same time. Inparticular, when SA and data are reserved together, both the SA and thedata can be reselected. The SA is transmitted in a manner of includinginformation on whether or not the SA and the data are reserved. In thiscase, reservation/reselection can be performed on both the SA and thedata. Once the SA and the data are determined by sensing, if it ischecked that a collision occurs on either the SA or the data, a resourceselection change (reselection) is performed on both the SA and the data.In particular, according to the abovementioned method, if the SA and thedata are reserved, since an SA resource and a data resource aremaintained, it may be able to stably estimate an amount of interferenceaffecting a different UE. In addition, if reselection of the SA andreselection of the data are performed at the same time, it may be ableto prevent unnecessary reselection and stably measure interference of aUE.

It may indicate reservation of the SA and reservation of the data,respectively. It may be able to transmit the SA in a manner of includingreservation (SPS or message generation) periods of the SA and the dataand information indicating whether or not the SA and the data arereserved in the SA. According to the present method, information onwhether or not an SA resource transmission is maintained in a next SPSperiod and information on whether or not a data resource transmission ismaintained can be transmitted in a manner of being included in the SA.According to the present method, since resource selection maintenanceinformation is most flexibly included, when a collision occurs on theSA, the data, or both the SA and the data, it may be able to directlyindicate whether to perform reselection. For example, if a collisionoccurs on a resource of the SA due to a different UE, information onwhether to perform reservation of the SA is released. Hence, the SAperforms reselection in a next transmission and the data maintainsreservation and does not perform any separate reselection procedure. Inparticular, in this case, an indicator indicating whether or not aresource allocation of a current SA period is maintained in a nextmessage transmission can be transmitted in a manner of being included inthe SA using 1 bit according to the SA and the data. Nearby UEs are ableto know whether or not each of the SA and the data is reserved accordingto the indicator.

The SA randomly selects a resource, selects a resource according to apredetermined hopping pattern, or selects a resource by performingsensing to indicate whether or not data is reserved. In particular, SAtransmits information on whether or not the data is reserved. Accordingto the present method, the SA can select and transmit an SA resourcewhenever data is transmitted (every SA period). For example, a specificSA resource index interlocked with an SA ID is selected in every SAperiod and the selected specific SA resource index can be used for SAtransmission. Or, an SA resource can be randomly selected andtransmitted whenever data is transmitted. Or, an SA resource can beselected via sensing whenever data is transmitted. When SA resourceallocation is performed using sensing, if the same resource iscontinuously selected, a collision can be consistently occurred with aspecific UE having a similar sensing result. In order to prevent theconsistent collision, a resource can be randomly selected from among theremaining SA resources except a resource of energy less than aprescribed threshold or a resource preoccupied by a different UE. Or, aresource can be selected by a UE ID.

Meanwhile, SA can be transmitted according to a predetermined hoppingpattern (a hopping pattern for solving a half-duplex problem) wheneverdata is transmitted. In this case, an optimized resource can bedetermined by sensing among the hopping pattern. When energy of the SAis measured, SA resource positions where SA retransmission is performedare regarded as an SA resource group and measurement values are averagedto perform measurement of an SA resource. A UE knows an SA hoppingpattern according to an SA resource in advance, performs measurementaccording to an SA resource, and averages measurement according to an SAresource group in accordance with a hopping pattern of an SA resource.The UE randomly selects an SA resource from among a group of SAresources of which energy is equal to or less than X % to transmit SA.As an extreme case, the UE may select an SA resource group of leastenergy. The abovementioned method corresponds to a method that a meritof a method for a UE to randomly determine an SA resource is combinedwith a merit of a method of determining an SA resource by sensingenergy. If an SA resource is determined by measuring energy only, it isunable to completely solve a half-duplex problem of SA between UEs. Whenan SA resource is randomly determined whenever data is transmitted,although a data resource is determined based on sensing, SA transmissionrandomly occurs and reception performance of data can be degraded due toin-band emission. If the half-duplex problem of the SA is solved,optimized energy is identified and transmitted, and the optimized energyis maintained during a prescribed data transmission period, data sensingcan be stably performed as well.

Meanwhile, a reservation period of data and a reservation period of SAcan be configured by a different period. For example, the data performsreservation during 1000 ms, whereas the SA can perform reservation inevery 200 ms.

Meanwhile, when a UE measures interference of a nearby UE, the UE canmeasure the interference via SA decoding, measure energy of data, ormeasure energy of SA. A network can signal a method of performingsensing among the abovementioned methods to a UE via physical layersignaling or higher layer signaling. If each of the methods isconfigured to be used, the network can signal a related threshold/limitvalue parameter to the UE. For example, the network can indicate aspecific region or specific UEs to perform SA decoding-based sensing.Or, the network can indicate the specific UEs to use both SA decodingand data energy measurement. The UE can select resources of which energyis less than a prescribed threshold from among the remaining resourcesexcept a resource occupied via SA decoding. Or, the network can indicateresource selection to be performed using energy measurement of dataonly. In this case, the UE can perform resource selection/reselectionbased on the energy measurement of data.

Measurement and Signaling of F-Node

An F-node performs measurement and informs a UE of a measurement value.Or, the F-node can signal a UE behavior based on a measurement of a UE.By doing so, it may be able to reduce a problem of differentlydetermining a current channel state. The problem may occur when thetiming of performing measurement and/or a position of a UE performingmeasurement is different. For example, the F-node collects measurementresults of UEs and can determine a behavior of a UE of a correspondingregion. More specifically, it may consider a method described in thefollowing.

The F-node measures congestion near the F-node and can signal themeasured congestion to a V-UE. The F-node measures RSSI or a busy levelof a channel (e.g., when the F-node measures RSRP of an RS transmittedby a UE, a ratio of exceeding a predetermined threshold or time ofexceeding a threshold in a specific window) and can signal the RSSI orthe busy level of the channel to a V-UE and/or a P-UE via physical layersignaling or higher layer signaling. The UE does not simply use thevalue measured by the F-node as it is. Instead, the UE shares themeasurement value with nearby F-nodes via a wired backhaul (e.g., X2interface or a separate wired backhaul) or an air interface and thenearby F-nodes signal the measurement value to the UE. In particular,each of the F-nodes averages measurement values with the nearby F-nodesor a UE behavior (or, UE state) (in case of a behavior/UE state, acommon behavior is determined) and signal the averaged measurement valueto the UE.

The UE performs weighted average on the measurements measured by each ofthe F-nodes to make nearby UEs have a common behavior of a certainlevel. For example, when two F-nodes (F-nodes 1 and 2) are examined andreception strength of a signal received from each of the F-nodescorresponds to A and B [Watt], the UE can smooth the measurement valuesby determining (A*F-node 1's measurement+B*F-node 2'smeasurement)/(A+B). In this case, it is not restricted to the weightaverage of the two measurement values. It may also be able to performmeasurement (weighted) averaging on an F-node at which signal strengthequal to or greater than a prescribed threshold is received.

The UE does not use the value signaled by the F-node as it is. The UEcan determine a final behavior by using a value measured by the UE aswell as the value signaled by the F-node. If the measurement measured bythe UE is not reflected, since actual measurement is not reflected, itis not preferable. A ratio of reflecting the measurement measured by theUE can be signaled by a network or the F-node via physical layersignaling or higher layer signaling. For example, the ratio can bedifferentiated according to density of F-nodes in a specific region. Ifdensity of F-nodes is high, a higher weight is applied to a measurementvalue signaled by an F-node. If density of F-nodes is low, a lowerweight is applied to a measurement value signaled by an F-node.

Method of determining UE behavior determined by UE

If a frequency (message generation period) of transmitting and/orreceiving a message is simply controlled by a load or congestion of achannel, inter message reception and/or transmission time of a specificUE can be extended. As mentioned in the foregoing description, if afrequency of transmitting and/or receiving a past message is equal to orless than a prescribed level, it may consider a method that the specificUE increases the frequency again. In particular, a UE can determine acurrent behavior with reference to a past behavior to preventperformance degradation of a specific UE instead of determining abehavior of the UE in consideration of a load or congestion of a currentchannel.

For example, if a UE is previously configured to transmit a message witha long specific time period (message generation period), it may be ableto determine a rule that the UE performs transmission with a shortmessage generation period. As a different example, if a UE is previouslyconfigured with Tx power of A dBm during a specific time period, it maybe able to determine a rule that the UE performs transmission with Txpower of B dBm after the specific time period is elapsed. Theabovementioned operation can be applied not only to a transmissionoperation of a message but also to a reception operation of a message.If it fails to receive a message of a specific type during prescribedtime, it may extend a length of a reception window of the message orconfigure a period for monitoring the message to be short to increase areception rate.

Monitoring Method of P-UE

In case of a P-UE, due to a battery problem, it might be a burden forthe P-UE to always perform monitoring. Hence, the P-UE mayintermittently wake up and perform a monitoring operation. In this case,it may consider specific operations described in the following.

As a first operation, a transmission pool or a reception pool for theP-UE only can be signaled by an F-node via physical layer signaling orhigher layer signaling or can be determined in advance. Meanwhile, aresource pool for the P-UE can be configured with a relatively longperiod in consideration of battery consumption of the P-UE (e.g., 1second, 100 ms section). P-UEs may assume that a V-UE does not performtransmission in a transmission pool for the P-UE only. The P-UE performssensing in the transmission pool for the P-UE only and may be then ableto perform transmission. In this case, no UE may perform transmission inan initial partial section of the pool for the P-UE. Hence, all or apart of UE behavior parameters can be differently configured in thetransmission pool for the P-UE in a manner of being different from thoseof a V-UE. Or, all or a part of UE behavior parameters can be configuredin a manner of being different from a V-UE according to a UE typeirrespective of the pools of the P-UE and the V-UE. In order to preventa case that no P-UE performs transmission in the initial part of thepool, P-UEs may randomly determine a resource and transmit a signal inthe initial partial section (or, a resource used by the P-UE) of thepool for the P-UE or it may configure a predetermined sequence or acodeword to be transmitted at a random time position. By doing so, itmay be able to configure other P-UEs to identify an approximate level ofcongestion. Meanwhile, it may be able to configure the P-UE not totransmit an SLSS in every SLSS transmission period for a battery savingoperation. To this end, the P-UE can perform SLSS transmission in anSLSS resource closest to the forepart of the resource pool for the P-UE,the N number of SLSS resources close to the forepart of the pool for theP-UE, and/or an SLSS resource within the resource pool configured forthe P-UE. The SLSS transmitted by the P-UE is distinguished from an SLSStransmitted by a V-UE using a format of the SLSS or an ID of the SLSS.The SLSS transmitted by the P-UE can be indicated via a PSBCH field. Or,the SLSS transmitted by the P-UE can be transmitted using an IDindicated by an RSU or PSBCH.

As a second operation, if all P-UEs are aligned with a transmission poolfor a P-UE only, the P-UEs may fail to listen to a mutual signal due toa half-duplex constraint. Or, due to in-band emission between P-UEs, itmay be difficult for other UEs to smoothly receive a signal. In order tosolve the problems, the transmission pool of the P-UE is divided intothe N number of sub-pools (or, a period of a specific P-UE group amongthe transmission pool of the P-UE can be divided in advance) andtransmission can be performed in a different sub-pool. A P-UE performsmonitoring in sub-pools except a sub-pool in which the P-UE performstransmission to identify an approximate level of congestion. Thesub-pool in which the P-UE performs transmission can be randomlydetermined. A value resulted from performing modular N on an ID of theP-UE can be used as a seed value for determining a sub-pool of the P-UE.Or, an F-node may signal an index of a sub-pool in which the P-UEperforms transmission or a seed value for selecting a sub-pool viaphysical layer signaling or higher layer signaling. Or, when a method ofselecting a pool is determined in advance based on signal strength of aspecific F-node or signal strength of a UE, if a specific condition issatisfied, a corresponding pool can be used. In this case, in order toprevent a transmission from being continuously performed in the same UEgroup and the same sub-pool, a sub-pool can be randomly selected inevery period. Or, it may hop a sub-pool using an SA ID of a UE.

As a third operation, when a P-UE (intermittently) wakes up with aperiod longer than a period of a V-UE and receives a message, if theP-UE fails to receives a V2X message or a relatively important message(e.g., a security message), the P-UE may additionally wake up andattempt to receive the message. For example, if density of vehicle UEsis very high, a transmission period of a V-UE may become longer or amessage can be more frequently transmitted. In this case, assume that aP-UE performs an operation of receiving a signal of the V-UE by wakingup 100 ms of 1 second. Yet, in this case, since density of the V-UE istoo high, the P-UE may fail to properly receive a message. In this case,the P-UE additionally wakes up as much as 100 ms and attempts to receivethe message. If a message is identical to the message of the previous100 ms, the P-UE may attempt to combine the messages. Or, the P-UE mayreceive the message using a new scheme. By doing so, the P-UE canreceive messages of more V-UEs. The wake up time extension extended bythe P-UE according to a reception rate can be determined in advance or anetwork can configure all or a part of an interval of the wake up time,a section length, and a length of additional wake up time according tooccurrence of congestion. In this case, in order to distinguish a caseof failing to receive a message from a case of not transmitting amessage at all, when specific SA or data measures high energy or RSpower, if it fails to receive data on a corresponding channel, it can beregarded as the case of failing to receive a message. Moreover, whenenergy sensing or SA is read in advance, it is anticipated that data isto be received in a corresponding resource region, and decoding isperformed, if CRC is failed, it can be regarded as a case that a messageis transmitted but it fails to receive the message. If a messagereception rate or the number of not received messages is equal to orgreater than a prescribed threshold, wake up time is additionallyextended to attempt to additionally receive a V2X message. To this end,it may explicitly signal a type of a reception message to a different UEvia SA. Or, it may differently configure a physical layer format (DMRSsequence, CS, or OCC is differently configured according to a messagetype) or an explicit physical layer indicator can be transmitted in amanner of being included in a certain region of a data RE.

As a fourth operation, if a P-UE fails to receive a message of aspecific type during a wake up time window, the P-UE additionally wakesup and can perform a receiving operation. For example, if the P-UE failsto receive a security message among an event triggered message and aperiodic message, the P-UE additionally wakes up and may attempt toreceive the security message.

As a fifth operation, when a P-UE performs reception in a predeterminedwake up window, if the P-UE fails to receives a message in the windowduring prescribed time (in this case, in order to distinguish a case offailing to listen to a message due to the lack of the message from acase of failing to listen to a message due to severe interference, acase of failing to receive a message when a signal energy level is equalto or greater than a prescribed threshold (in this case, an energy levelthreshold/limit can be determined in advance or can be configured by anetwork)), it may reduce a wake up interval of the P-UE to make the P-UEmore frequently wake up and listen to a message. In this case, the wakeup interval can be determined in advance or can be configured by anetwork. If a specific condition (e.g., the number of messages receivedduring wake up time, a reception rate less than a certain threshold),which is determined in advance or configured by a network, is satisfied,a UE configures the wake up interval to be short to attempt toadditionally receive a V2X message.

As a sixth operation, although it is able to make a length of a windowin which a P-UE performs wake up vary, a period for which the P-UEperforms wake up can also be differently configured according tosurroundings or a status of a UE to reduce battery consumption to acertain level. For example, if the P-UE receives a message during 500 msfor a certain reason, a wake up interval of the P-UE can be configuredto be longer (e.g., 5 seconds) than 500 ms in consideration of batteryconsumption. If congestion occurs and a nearby V-UE modifies a messagegeneration period to be long, a P-UE is unable to receive all signals ofneighboring V-UEs at a time. In this case, it is preferable to align amessage reception window in which the P-UE wakes up and listens to asignal with the message generation period of the V-UE. Yet, in thiscase, battery consumption of the P-UE may excessively increase. Hence, amessage reception period of the P-UE is increased together to mitigate aburden for the battery consumption of the P-UE.

As a seventh operation, a message transmission period and/or a messagereception period or a message transmission window size and/or a messagereception window size may vary according to mobility of a P-UE. Forexample, a P-UE may move fast using a bicycle or a differenttransportation means. In this case, a message transmission and/orreception window/period can be differently configured according to astate or status of the P-UE. For example, if a P-UE recognizes asituation that the P-UE is getting on a vehicle or the P-UE receives anindication indicating the situation from a higher layer, the P-UE canperform a message generation transmission/reception operation similar tothat of a V-UE. As a different example, if a P-UE recognizes a situationthat the P-UE is getting on a bicycle or the P-UE receives an indicationindicating the situation from a higher layer, the P-UE may morefrequently wake up and listen to a message of a nearby V-UE. Or, theP-UE may perform an operation of receiving a message of a V-UE for along time.

As an eighth operation, when a mode of a P-UE is changed according tomobility, status, or an indication of a higher layer, the P-UE ma use aseparate resource pool different from a transmission pool used by alegacy P-UE or a V-UE. For example, if a higher layer informs a UE thatthe UE is getting on a vehicle, although the UE corresponds to a P-UE,the UE may follow a resource pool and a behavior of a V-UE. Inparticular, when a V2X operation is performed, a behavior of a UE is nota unique characteristic of the UE. The behavior of the UE can be changedby an indication indicated by a higher layer signal. If it is able tochange the behavior of the UE according to a state of the UE, it is ableto perform an optimized operation in accordance with the status of theUE. To this end, the present invention proposes a method that a higherlayer (e.g., application layer) recognizes a status of a UE andtransmits an indicator for reflecting the status of the UE to a physicallayer operation or a MAC layer operation. In order to perform theabovementioned operation, a network can determine a behavior level of aUE in advance. If the UE informs the network of a status of the UE,surrounding interference information, and the like, the network canindicate the UE to operate with a specific behavior. Or, the network cansignal an operation to be performed by the UE according to environmentto which the UE belongs thereto to the UE in advance via physical layersignaling or higher layer signaling. If the UE faces the situation, theUE can operate with the behavior indicated by the network. For example,when a P-UE is getting on a vehicle or a bicycle, if the P-UE recognizesthe situation, the P-UE reports a measurement to a network, or thenetwork configures a behavior of the P-UE in advance for the situation,the P-UE can operate with the behavior configured for the situation.

Meanwhile, a reception UE may or may not listen to a signal according toa transmission UE type or a message type. Battery consumption of thereception UE can be reduced by making a physical layer distinguish thecases from each other. To this end, a type of a UE and/or a message typecan be transmitted in a manner of being explicitly included in an ID ofSA or SA. Or, it may be able to differently configure a DMRS sequence orit may be able to transmit an indicator indicating a UE type and/or amessage type in a manner of including the indicator in a partial regionof data. For example, it may be not necessary for a P-UE to listen to asignal of a different P-UE. To this end, a UE can transmit an indicatorindicating whether the UE corresponds to a P-UE or a V-UE by includingthe indicator in SA. In a broad sense, the UE can transmit a differentindicator according to a message type or a packet type. For example,among messages transmitted by a V-UE, one message can be transmitted fora P-UE and another one can be transmitted for the V-UE. In particular,in order to make a reception UE not to perform an unnecessary receptionoperation according to a type of a message, a method of dividing aresource region into sub-resource regions and/or a method distinguishingthe sub-resource regions from each other in a physical layer areproposed. The two methods can be implemented in a manner of beingcombined or can be implemented independently. If a message type or a UEtype is determined in advance according to a resource region, it is notnecessary for a UE to receive the whole of the resource region, therebyconsiderably reducing power consumption. Or, although a resource regionis not divided, when SA of an SA pool is received, if SA of a UE, whichis not necessary to listen to, is received, since data decoding is notperformed, power consumption of a UE can be reduced.

Meanwhile, a P-UE may fail to receive such a message transmitted with arelatively long period as a security message among messages transmittedby a V-UE. For example, when the V-UE transmits a periodic message inevery 100 ms and transmits a security message in every 500 ms, the P-UEmay listen to messages received during 100 ms only by temporarily wakingup due to a better consumption issue. In this case, the P-UE may fail toreceive the security message. In this case, the present inventionproposes a method that an eNB or an RSU broadcasts a security message ofa nearby V-UE. The eNB or the RSU may signal a security message of aV-UE to a P-UE via separate physical layer signaling or higher layersignaling. Although the P-UE is unable to receive security messages ofall V-UEs while waking up, the P-UE is able to interpret the message ofthe V-UE using a message signaled by the eNB or the RSU.

Meanwhile, all or a part of the proposed operations are not restrictedto operations of a P-UE. The proposed operations can be extensivelyapplied to a V-UE as well. On the contrary, an operation of the V-UE canbe applied to the P-UE as well.

Examples for the aforementioned proposed methods can also be included asone of implementation methods of the present invention. Hence, it isapparent that the examples are regarded as a sort of proposed schemes.The aforementioned proposed schemes can be independently implemented orcan be implemented in a combined (aggregated) form of a part of theproposed schemes. It may be able to configure an eNB to inform a UE ofinformation on whether to apply the proposed methods (information onrules of the proposed methods) via a predefined signal (e.g., physicallayer signal or upper layer signal).

Configurations of Devices for Embodiments of the Present Invention

FIG. 12 is a diagram for configurations of a transmitter and a receiver.

Referring to FIG. 12, a transmit point apparatus 10 may include areceive module 11, a transmit module 12, a processor 13, a memory 14,and a plurality of antennas 15. The antennas 15 represent the transmitpoint apparatus that supports MIMO transmission and reception. Thereceive module 11 may receive various signals, data and information froma UE on an uplink. The transmit module 12 may transmit various signals,data and information to a UE on a downlink. The processor 13 may controloverall operation of the transmit point apparatus 10.

The processor 13 of the transmit point apparatus 10 according to oneembodiment of the present invention may perform processes necessary forthe embodiments described above.

Additionally, the processor 13 of the transmit point apparatus 10 mayfunction to operationally process information received by the transmitpoint apparatus 10 or information to be transmitted from the transmitpoint apparatus 10, and the memory 14, which may be replaced with anelement such as a buffer (not shown), may store the processedinformation for a predetermined time.

Referring to FIG. 12, a UE 20 may include a receive module 21, atransmit module 22, a processor 23, a memory 24, and a plurality ofantennas 25. The antennas 25 represent the UE that supports MIMOtransmission and reception. The receive module 21 may receive varioussignals, data and information from an eNB on a downlink. The transmitmodule 22 may transmit various signals, data and information to an eNBon an uplink. The processor 23 may control overall operation of the UE20.

The processor 23 of the UE 20 according to one embodiment of the presentinvention may perform processes necessary for the embodiments describedabove.

Additionally, the processor 23 of the UE 20 may function tooperationally process information received by the UE 20 or informationto be transmitted from the UE 20, and the memory 24, which may bereplaced with an element such as a buffer (not shown), may store theprocessed information for a predetermined time.

The configurations of the transmit point apparatus and the UE asdescribed above may be implemented such that the above-describedembodiments can be independently applied or two or more thereof can besimultaneously applied, and description of redundant parts is omittedfor clarity.

Description of the transmit point apparatus 10 in FIG. 12 may be equallyapplied to a relay as a downlink transmitter or an uplink receiver, anddescription of the UE 20 may be equally applied to a relay as a downlinkreceiver or an uplink transmitter.

The embodiments of the present invention may be implemented throughvarious means, for example, hardware, firmware, software, or acombination thereof.

When implemented as hardware, a method according to embodiments of thepresent invention may be embodied as one or more application specificintegrated circuits (ASICs), one or more digital signal processors(DSPs), one or more digital signal processing devices (DSPDs), one ormore programmable logic devices (PLDs), one or more field programmablegate arrays (FPGAs), a processor, a controller, a microcontroller, amicroprocessor, etc.

When implemented as firmware or software, a method according toembodiments of the present invention may be embodied as a module, aprocedure, or a function that performs the functions or operationsdescribed above. Software code may be stored in a memory unit andexecuted by a processor. The memory unit is located at the interior orexterior of the processor and may transmit and receive data to and fromthe processor via various known means.

Preferred embodiments of the present invention have been described indetail above to allow those skilled in the art to implement and practicethe present invention. Although the preferred embodiments of the presentinvention have been described above, those skilled in the art willappreciate that various modifications and variations can be made in thepresent invention without departing from the spirit or scope of theinvention. For example, those skilled in the art may use a combinationof elements set forth in the above-described embodiments. Thus, thepresent invention is not intended to be limited to the embodimentsdescribed herein, but is intended to accord with the widest scopecorresponding to the principles and novel features disclosed herein.

The present invention may be carried out in other specific ways thanthose set forth herein without departing from the spirit and essentialcharacteristics of the present invention. Therefore, the aboveembodiments should be construed in all aspects as illustrative and notrestrictive. The scope of the invention should be determined by theappended claims and their legal equivalents, and all changes comingwithin the meaning and equivalency range of the appended claims areintended to be embraced therein. The present invention is not intendedto be limited to the embodiments described herein, but is intended toaccord with the widest scope consistent with the principles and novelfeatures disclosed herein. In addition, claims that are not explicitlycited in each other in the appended claims may be presented incombination as an embodiment of the present invention or included as anew claim by subsequent amendment after the application is filed.

INDUSTRIAL APPLICABILITY

The embodiments of the present invention can be applied to variousmobile communication systems.

1. A method of receiving or transmitting data, by a UE in a wirelesscommunication system, comprising the steps of: receiving controlinformation through a control channel, and receiving or transmitting afirst data based on a first frequency resource indicated by the controlinformation, wherein the control information includes information bitsindicate both an interval and whether the control informationtransmitting UE keeps the first frequency resource, wherein the UEreceives a second data from the control information transmitting UE on asecond frequency resource having same frequency location with the firstfrequency resource in last subframe within the interval, when theinformation bits indicate the control information transmitting UE keepsthe first frequency resource and the first data indicated by the controlinformation is transmitted to the UE, wherein the UE transmits a thirddata on a third frequency resource having different frequency locationwith the first frequency resource in last subframe within the interval,when the information bits indicate the control information transmittingUE keeps the first frequency resource and the first data indicated bythe control information is not transmitted to the UE, wherein theinterval is determined by a value selected by the UE from among aplurality of values and wherein the plurality of the values are allowedby a period-related parameter forwarded via higher layer signaling. 2.The method of claim 1, wherein the period-related parameter istransmitted from an F-node (fixed node) related to the UE.
 3. The methodof claim 1, wherein if the second data corresponds to a retransmissionof the first data, the second data is transmitted within aretransmission count.
 4. The method of claim 3, wherein theretransmission count is forwarded to the UE via higher layer signaling.5. The method of claim 1, wherein MCS within a range indicated by higherlayer signaling is used to transmit the first data.
 6. The method ofclaim 5, wherein the MCS is used when speed of the UE is equal to orless than a threshold.
 7. The method of claim 6, wherein the speed equalto or less than the threshold is forwarded via higher layer signaling.8. (canceled)
 9. A UE in a wireless communication system, comprising: atransmitter and a receiver; and a processor, the processor receivescontrol information through a control channel and transmits or receivesa first data based on a first frequency resource indicated by thecontrol information, wherein the control information includesinformation bits indicate both an interval and whether the controlinformation transmitting UE keeps the first frequency resource, whereinthe UE receives a second data from the control information transmittingUE on a second frequency resource having same frequency location withthe first frequency resource in last subframe within the interval, whenthe information bits indicate the control information transmitting UEkeeps the first frequency resource and the first data indicated by thecontrol information is transmitted to the UE, wherein the UE transmits athird data on a third frequency resource having different frequencylocation with the first frequency resource in last subframe within theinterval, when the information bits indicate the control informationtransmitting UE keeps the first frequency resource and the first dataindicated by the control information is not transmitted to the UE,wherein the interval is determined by a value selected by the UE fromamong a plurality of values and wherein the plurality of the values areallowed by a period-related parameter forwarded via higher layersignaling.
 10. The UE of claim 9, wherein the period-related parameteris transmitted from an F-node (fixed node) related to the UE.
 11. The UEof claim 9, wherein if the second data corresponds to a retransmissionof the first data, the second data is transmitted within aretransmission count.
 12. The UE of claim 11, wherein the retransmissioncount is forwarded to the UE via higher layer signaling.
 13. The UE ofclaim 1, wherein MCS within a range indicated by higher layer signalingis used to transmit the first data.
 14. The UE of claim 13, wherein theMCS is used when speed of the UE is equal to or less than a threshold.15. The UE of claim 14, wherein the speed equal to or less than thethreshold is forwarded via higher layer signaling.